This invention relates generally to a film cassette containing a plurality of film units usable in a photographic apparatus and, more particularly, to a cassette which can be removed from the apparatus without admitting light to the sensitive areas of unexposed film units as well as facilitating the distinguishing of exposed and unexposed film units.
Often photographers desire to remove a film cassette from a camera before all the film frames have been exposed. This may occur when the photographer wishes to replace a cartridge having color film, with a cartridge containing black-and-white film or vice versa.
Several techniques have been developed for purposes of insuring proper reuse of cartridges so that the original exposures are not double exposed or unexposed film frames are wasted. One known approach is described in U.S. Pat. No. 4,034,393. This patent describes a continuous strip of film storable in a cylindrical type cartridge and includes tabs and labels for purposes of distinguishing between exposed and unexposed film frames. In this regard, the tab prevents the leader end of the film strip from being rewound entirely into the cassette while the label allows recording of the number of exposed frames. Exemplary of other approaches in this area are those described in the following U.S. Pat. Nos.: 4,311,377 and 4,324,469.
Other cameras of the self-developing type are configured for exposing and processing positive image transparency units (i.e., instant slides). Examples of such cameras are shown in the following commonly-assigned U.S. Pat. Nos: 2,854,903; 3,255,670; 3,350,990; 3,369,469; 3,369,470; 3,421,423; 3,437,023; 3,437,024; 3,446,127; 3,446,131; 3,455,222; 3,541,939; 3,541,940; 3,541,937; 3,541,938; 3,575,081; 3,525,293; 3,614,920; 3,648,527; and 3,636,844.
To varying degrees these cameras require that the photographer manually handle the transparency after processing. Of course, this increases the possibility of it becoming damaged. Moreover, the user must interrupt his picture taking to remove the processed slide and find a dirt and dust-free environment for its storage. The camera described in U.S. Pat. No. 3,350,990 has an imbibition chamber large enough to receive all the exposed film units. But if the user wishes to view his results before taking the next picture, he must remove the slide for viewing and then manually reinsert the slide for storage.
The camera described in U.S. Pat. No. 2,854,903 uses a transparency film unit having a strippable opaque backing sheet for preventing exposure to the underlying sheets in the unexposed stack of film units.
In U.S. Pat. No. 3,541,940 there is disclosed a film magazine having a supply chamber containing unexposed film units and a storage chamber for storing exposed film units. However, such an approach requires the user to manually remove the slide from the camera imbibition chamber and insert it into the magazine storage chamber.
Commonly-assigned U.S. Pat. No. 4,114,166 requires two removable chambers, one for unexposed film units and the other for exposed film units; however, the user need not touch the transparency. Commonly-assigned U.S. Pat. No. 4,265,525 discloses use of a disc carrying small format positive transparencies being rotatable in a camera and having separate exposing and viewing stations, whereby not all of the film units need be exposed.
None of the known foregoing cameras especially of the self-developing type use individual self-developing film units and make provision for a single removable cassette which can house both exposed and unexposed film units, let alone distinguishing between unexposed and exposed film units in such a container.